The present invention relates to a technology of personal authentication in which features are obtained from biological information by frequency analysis and personal authentication is performed based on the similarity between the features.
As individual identification techniques using human biological information (biometrics), there have been proposed many methods using information of fingerprints, irises, blood-vessel arrangements in the retinas, faces, and the like. Among these, individual identification using an iris, in particular, is expected to be mainstream of biometrics authentication in the future for the reasons that:
(1) an iris pattern can be acquired with a camera in a noncontact manner,
(2) the false acceptance rate (FAR) is significantly low due to complexity of the iris pattern, and
(3) the iris pattern remains unchanged substantially through the life of the owner.
Techniques for extracting iris features from iris images and identifying individuals are disclosed in U.S. Pat. No. 5,291,560, Japanese National Phase PCT Laid-Open Publication No. 8-504979, and “High Confidence Visual Recognition of Persons by a Test of Statistical Independence”, IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 15, No. 11, November 1993 (these three disclosures are roughly the same in contents).
In the above techniques, an iris image is analyzed at multiple resolutions using multi-scale self-similarity type two-dimensional quadrature band-pass filters (Gabor filters, for example) to generate a feature (iris code). To state as a specific procedure, a digitized image of a human eye is captured with a video camera, and the boundary between the iris and the sclera and the boundary between the iris and the pupil are determined to separate an iris region from others. A polar coordinate system is applied to the separated iris image, and a plurality of ring analysis bands are determined. Analysis and coding are then performed for the analysis bands using a signal processor comprised of multi-scale quadrature band-pass filters. The thus-generated iris codes are compared with each other by calculating a hamming distance between the codes as shown in FIG. 24, to determine whether or not the compared iris codes originate from an identical person.